‘We didn’t want it to be over:’ How the Celtics marched past the defending champs and into the Eastern Conference finals

Marcus Smart was one of the many Celtics who set the TD Garden crowd ablaze on Sunday, his double-double part of another calling-card performance by the defense.Jim Davis/Globe Staff

Although the noise is almost always there, Celtics coach Ime Udoka insists that he hardly ever notices it. Amid the cheering and screaming and stomping, he is so focused on his task, so focused on the game, so focused on his players, that all he hears is silence.

When the Celtics pushed ahead of the Bucks by 20 points midway through the fourth quarter of Game 7 on Sunday, Udoka could see his players were getting caught up in the moment, and who could blame them? But the coach was still cautious.

“Guys, let’s finish,” he said. “It’s not over yet.”

A few minutes later, though, the demolition was so thorough and time was so scarce that Udoka could finally allow himself a moment to exhale. He could finally allow himself a moment to just stop and listen.

“Everybody’s talked about how loud it’s been in here, and I never heard it until tonight,” he said. “I guess you take the time to appreciate it when it’s a 20-something point game with two minutes to go. You’re hearing the crowd and looking around and seeing everyone standing. That was the first time I really felt it in the series.”

They continued to rejoice until the very end, until Celtics 109, Bucks 81 glowed on each scoreboard around TD Garden.

This Boston team was once in danger of missing the playoffs altogether. Just two days ago it went to Milwaukee, the scars from its Game 5 collapse still visible, facing elimination.

Now, it is now marching on to the Eastern Conference finals, where it will face the top-seeded Heat. Game 1 will be Tuesday night in Miami.

“We had two games where our season was on the line, and we didn’t want it to be over,” Celtics forward Jaylen Brown said. “We didn’t overcome all the stuff we did earlier in the season for this to be it.”

With Sunday's game well in hand, Grant Williams, Jayson Tatum, and Jaylen Brown watch the backups finish off the Bucks.Barry Chin/Globe Staff

The Celtics’ formula for Sunday’s win was not typical. They did not hop on the backs of Brown and Jayson Tatum. Instead, they turned to forward Grant Williams, and told him to start launching.

Boston’s fleet of weapons creates tough decisions for opposing defenses, and Milwaukee decided in this series it would force the Celtics’ secondary players to beat them from the perimeter. In Game 7, that approach became particularly excessive.

Milwaukee deployed its big men on Williams and essentially dared him to make a shot by sagging back in the paint. He made his first, but then had a pair of awkward misses as Boston fell behind by 10 points. Udoka could see that he was uneasy.

“I told him, ‘Let them fly. They’re disrespecting you more tonight than earlier in the series,’ ” Udoka said.

That sentiment was shared by the rest of the team whenever Williams went to the bench.

“It’s tough to get in your own head when your entire team, like 15 people, walk up to you and say, ‘Keep shooting,’ ” Williams said. “So for me, it was just like, all right, they’re encouraging it, might as well take advantage.”

Williams finished the game 7 for 18 from the 3-point line en route to a game-high 27 points. He broke the NBA record for Game 7 3-point attempts, previously held by Warriors sharpshooter Stephen Curry.

“I call him Grant Curry now,” Brown quipped.

Tatum finished with 23 points and Brown added 19 for Boston. But the game’s most important stretch came when Tatum was not even on the floor. He went to the bench after collecting his fourth foul with 7:44 left in the third period and Boston leading by 10 points. It was a dangerous scenario.

By the time the quarter ended, the Celtics had actually pushed their advantage to 79-64.

“That was huge,” Tatum said. “The way that they played together, moved the ball, made the right plays on both ends and extended the lead, I was extremely happy and excited watching the guys from the bench.”

The Celtics’ offense was sufficient, but the defense — this team’s calling card — was superb. The Bucks mustered just 55 points in the final three quarters, and the wear and tear on superstar Giannis Antetokounmpo finally began to show.

Milwaukee's Giannis Antetokounmpo was swarmed -- and slowed -- by Celtics' defenders most of the afternoon.Barry Chin/Globe Staff

Antetokounmpo finished with 25 points, 20 rebounds, and 9 assists, but a good chunk of that damage was inflicted in the opening quarter, when the Bucks climbed to an early lead. He labored through the second half and began to miss layups that he normally converts with little trouble.

Antetokounmpo played admirably throughout this series with fellow All-Star Khris Middleton sidelined with a sprained knee, but he just didn’t have sufficient help. The Bucks were 4 for 33 from the 3-point line.

After the Celtics’ Game 5 collapse at TD Garden, there were questions about whether this series would even return to this building and give Boston a chance at something more.

But now, this team has disposed of Kevin Durant and the Nets in a sweep, and Antetokounmpo and the defending NBA champions in seven rough, bruising games. It’s impossible not to see that there is a clear path to something even bigger.

With just under three minutes left in the game, the crowd broke into a ‘Beat the Heat’ chant. That will be Boston’s task now. The Heat defeated the Celtics in the 2020 conference finals in the Orlando bubble before going on to lose to the Lakers in the Finals.

“I expect nothing less than a great battle,” Brown said.